Marathons in altitude.

PURPOSE: We examined the effect of altitude up to 5200 m on marathon (42,195 m) performances. METHODS: Eight elite and four good runners participated in a marathon at 4300-m altitude (A1), and five elite runners participated both in A1 and in a marathon at 5200-m altitude (A2). The maximal aerobic power (VO2max) was determined indirectly in altitude during A1 and A2 expeditions from the scores of a 12-min running test. The fractions of VO2max utilized during both races were calculated from the linear relationship between running speed and VO2 described by Costill and Fox (1969). RESULTS: VO2max significantly decreases with altitude (P<0.001). We found a linear relationship (R2 = 0.73, P<0.001) between the speed of each participant in the sea level marathon and the speed of A1. The mean difference between the sea level and the A1 speed was 35+/-9% (P<0.001). In A1, elite runners utilized 63+/-8% whereas good runners utilized 52+/-8% of VO2max (P<0.001). The five elite runners utilized 74+/-6%; 67+/-1% (P< 0.01), and 71+/-3% (P<0.01) of their VO2max at sea level, A1, and A2, respectively. In Al, the mean heart rate (HR) was higher in elite than in good runners (P<0.001), whereas the percentage of maximum theoretical HR was 83+/-3% and 81+/-5%, respectively (P>0.05). CONCLUSIONS: Marathon performance in altitude is mainly affected by the lower VO2max. The better performance of elite marathoners in altitude compared with good runners was related to the higher % of VO2max maintained during every marathon. The differences between the expected and the observed performances at high altitude depend on the uneven running path and on a poorer economy of running that is related to the higher mechanical work of breathing. The fractional utilization of VO2max seems lowered by acute exposure to altitude and slightly increases with acclimatization.     

Influence of body mass and height on the energy cost of running in highly trained middle- and long-distance runners

Previous studies about the influence of body dimensions on running economy have not compared athletes specialized in different competition events. Therefore, the purpose of the present study was to assess the influence of body mass (m(b)) and height (h) on the energy cost of running (Cr) in 38 highly trained male runners, specialized in either marathon (M, n = 12), long middle-distance (5000 - 10000 m, LMD, n = 14) or short middle-distance (800 - 1500 m, SMD, n = 12), and to assess possible differences in body dimensions for each event. Subjects performed a progressive maximal exercise on the treadmill to determine oxygen uptake VO(2)) at different submaximal velocities and maximal oxygen uptake VO(2)max). Cr was calculated from VO(2) measurements. LMD runners had significantly higher mean Cr (0.192 +/- 0.007, 0.182 +/- 0.009, and 0.180 +/- 0.009 ml O(2) x kg(-1) x m(-1) for LMD, M and SMD, respectively) and VO(2)max (74.1 +/- 3.7, 68.5 +/- 2.9 and 69.7 +/- 3.4 ml x kg (-1) x min (-1)). Cr correlated with h (r = -0.86, p < 0.001) and m(b) (r = -0.77, p < 0.01) only in the SMD group. In conclusion, these data suggest that highly trained distance runners tend to show counterbalancing profiles of running economy and VO(2)max (the higher Cr, the higher VO(2) max and vice versa), and that anthropometric characteristics related with good performance are different in long-distance and middle-distance events.     

Running economy of African and Caucasian distance runners

PURPOSE: Anecdotal evidence suggests an advantageous physiological endowment of the African endurance athlete. Higher fractional utilization of VO2max has been suggested but not measured directly, and investigations of running economy have been inconclusive. The aim of the current study was to measure a) running economy and b) fractional utilization of VO2max, in African and Caucasian 10-km runners of similar body mass. METHODS: Eight African and eight Caucasian runners had no significant difference in mean race time (32.8 +/- 2.8, 32.0 +/- 2.5 min, respectively), body mass (61.4 +/- 7.0, 64.9 +/- 3.0 kg), age, body fat, or lean thigh volume. Caucasian runners were 6 cm taller (P < 0.05). Subjects completed a progressive treadmill VO2peak test. On a separate day, subjects completed two 6-min workloads (16.1 km x h(-1) and 10-km race pace) separated by 5 min. RESULTS: Mean VO2peak was 13% lower in the Africans (61.9 +/- 6.9, 69.9 +/- 5.4 mL x kg(-1) x min(-1), P = 0.01). At 16.1 km x h(-1), the Africans were 5% more economical (47.3 +/- 3.2, 49.9 +/- 2.4 mL x kg(-1) x min(-1), P < 0.05). This difference increased to 8% (P < 0.01) when standardized per kg(0.66). At race pace, the Africans utilized a higher %VO2peak (92.2 +/- 3.7, 86.0 +/- 4.8%, P < 0.01) and had higher HR (185 +/- 9, 174 +/- 11 b x min(-1), P < 0.05) and plasma [ammonia] (113.2 +/- 51, 60.3 +/- 16.9 micromol x L(-1), P < 0.05). Despite the higher relative workload, the plasma [lactate] was not different (5.2 +/- 2.0, 4.2 +/- 1.7 mmol x L(-1), NS). CONCLUSIONS: This study indicates greater running economy and higher fractional utilization of VO2peak in African distance runners. Although not elucidating the origin of these differences, the findings may partially explain the success of African runners at the elite level.     

Effect of training on the physiological factors of performance in elite marathon runners (males and females)

This study examined the effect of 8 weeks of specific marathon training before the Olympic trials on the physiological factors of the marathon performance in top-class marathon runners. Five males and four females, age 34 +/- 6 yr (+/- SD) with a marathon performance time of 2 h 11 min 40 s +/- 2 min 27 s for males and 2 h 35 min 34 s +/- 2 min 54 s for females, performed one test ten and two weeks before the trials. Between this period they trained weekly 180 +/- 27 km and 155 +/- 19 km with 11 +/- 7 and 7 +/- 0% of this distance at velocity over 10000 m for males and females, respectively. The purpose of this test was to determine in real conditions i. e. on level road: VO2 peak, the energy cost of running and the fractional utilisation of VO2 peak at the marathon velocity (vMarathon). They ran 10 km at the speed of their personal best marathon performance on a level road and after a rest of 6 min they ran an all-out 1000 m run. VO2 peak increased after the 8 weeks of pre-competitive training (66.3 +/- 9.2 vs 69.9 +/- 9.4 ml x min(-1) x kg(-1), p = 0.01). Moreover, since the oxygen cost of running at vMarathon did not change after this training, the fractional utilization (F) of VO2 peak during the 10 km run at vMarathon decreased significantly after training (94.6 +/- 6.2% VO2 peak vs 90.3 +/- 9.5% VO2 peak, p = 0.04). The high intensity of pre-competitive training increased VO2 peak and did not change the running economy at vMarathon and decreased the fractional utilization of VO2 peak at vMarathon.     

Applied physiology of marathon running

Performance in marathon running is influenced by a variety of factors, most of which are of a physiological nature. Accordingly, the marathon runner must rely to a large extent on a high aerobic capacity. But great variations in maximal oxygen uptake (VO2 max) have been observed among runners with a similar performance capacity, indicating complementary factors are of importance for performance. The oxygen cost of running or the running economy (expressed, e.g. as VO2 15 at 15 km/h) as well as the fractional utilisation of VO2 max at marathon race pace (%VO2 Ma X VO2 max-1) [where Ma = mean marathon velocity] are additional factors which are known to affect the performance capacity. Together VO2 max, VO2 15 and %VO2 Ma X VO2 max-1 can almost entirely explain the variation in marathon performance. To a similar degree, these variables have also been found to explain the variations in the 'anaerobic threshold'. This factor, which is closely related to the metabolic response to increasing exercise intensities, is the single variable that has the highest predictive power for marathon performance. But a major limiting factor to marathon performance is probably the choice of fuels for the exercising muscles, which factor is related to the %VO2 Ma X VO2 max-1. Present indications are that marathon runners, compared with normal individuals, have a higher turnover rate in fat metabolism at given high exercise intensities expressed both in absolute (m/sec) and relative (%VO2 max) terms. The selection of fat for oxidation by the muscles is important since the stores of the most efficient fuel, the carbohydrates, are limited. The large amount of endurance training done by marathon runners is probably responsible for similar metabolic adaptations, which contribute to a delayed onset of fatigue and raise the VO2 Ma X VO2max-1. There is probably an upper limit in training kilometrage above which there are no improvements in the fractional utilisation of VO2 max at the marathon race pace. The influence of training on VO2 max and, to some extent, on the running economy appears, however, to be limited by genetic factors.     

Running performance in middle-school runners

AIM: This study examined the relationship of 3-km run time to indices of aerobic and anaerobic ability in 9 male runners (13.4+/-0.6 years, mean+/-SD). METHODS: Anthropometric measurements were made, and an exercise test to determine running economy at 187 m x min(-1) and (.-)VO(2max) were assessed on a treadmill. On a separate day, 2 55-m sprints followed by a 3-km run were performed on a 200-m indoor track. Capillary blood samples were obtained from a finger tip immediately after the run to determine blood lactate level. Fractional utilization (%(.-)VO(2max) used during the 3-km run) was calculated. Correlations were used to examine the relationship between run time and the physiological measurements. RESULTS: Mean values for (.-)VO(2), HR and RER at maximal exercise were 61.7+/-4.4 ml x kg(-1)xmin(-1), 198.9+/-6.7 b x min(-1), and 1.16+/-0.04, respectively. The average time to run 3 km was 13.27+/-0.97 min (90.1+/-7.2% of (.-)VO(2max)). Post-run blood lactate level was 8.3+/-3.2 mmol x L(-1) and was significantly related (r=-0.73, p=0.02) to 3-km time. Fractional utilization tended to be related (r=-0.56, p=0.12) to time. CONCLUSIONS: In this age group the ability to run at a high percentage of (.-)VO(2max) and tolerate a high blood lactate appear to be important determinants of running performance in young male runners.     

Different hormonal response to continuous and intermittent exercise in middle-distance and marathon runners

In order to study the effects of different athletic backgrounds on exercise-induced hormonal responses, serum testosterone, luteinizing hormone, follicle-stimulating hormone and cortisol concentrations were measured before and after intensive continuous and intermittent running in well-trained middle-distance runners (MID) and marathon runners (MAR). They performed two 40-min exercises on a treadmill: a continuous run at an intensity of 80% [tempo run (TR)] and an intermittent run (IR) at an intensity of 100% of the velocity associated with VO(2max). The testosterone response to IR and the cortisol response to TR was higher (P<0.05) in MID compared with MAR. The testosterone response to IR correlated positively with the maximal blood lactate concentration achieved after the maximal running test (r=0.46, P<0.05, n=20), while the cortisol response to TR correlated negatively with the runner's VO(2max) (r=-0.62, P<0.05, n=20). In conclusion, a continuous running exercise resulted in a lower cortisol response in runners who are adapted for longer distances, and an intermittent running exercise resulted in a higher testosterone response in runners who are adapted to middle distances.     

Blood lactate accumulation during exercise in older endurance runners

To delineate the possible age-related differences in blood lactate response during exercise and its relations to endurance performance, 34 male runners (aged 21 to 69 years) performed an incremental treadmill running test. There were no significant differences in training distance and relative body fat among younger runners (YR), middle-aged runners (MR), and older runners (OR). The 5-km run time slowed with age, but was ranked at relatively the same level in each age group. OR had a 23% (P less than 0.001) and 12% (P less than 0.01) lower maximal oxygen uptake (VO2max) and a 22% (P less than 0.001) and 11% (P less than 0.001) slower 5-km run time than YR and MR, respectively. However, mean VO2 corresponding to 4 mM of blood lactate (OBLA VO2) was the same among the groups when expressed as %VO2max (YR; 84.3%, MR; 85.9%, OR; 85.9%). Significant correlations were found between OBLA VO2 (ml.kg-1.min-1) and 5-km run time in each group (YR; r = -0.648, P less than 0.05; MR; r = -0.658, P less than 0.01; OR; r = -0.680, P less than 0.05). These results suggest that OR attain a given blood lactate level at almost similar %VO2max to YR and MR and that OBLA VO2 in OR is useful for evaluating an endurance performance as well as in YR and in MR.     

Maximal and submaximal oxygen uptakes and blood lactate levels in elite male middle- and long-distance runners

Physiological characteristics of elite runners from different racing events were studied. Twenty-seven middle- and long-distance runners and two 400-m runners belonging to the Swedish national team in track and field were divided, according to their distance preferences, into six groups from 400 m up to the marathon. The maximal oxygen uptake (VO2 max, ml X kg-1 X min-1) on the treadmill was higher the longer the main distance except for the marathon runners (e.g., 800-1500-m group, 72.1; 5000-10,000-m group, 78.7 ml X kg-1 X min-1). Running economy evaluated from oxygen uptake measurements at 15 km/h (VO2 15) and 20 km/h (VO2 20) did not differ significantly between the groups even though VO2 15 tended to be lower in the long-distance runners. The running velocity corresponding to a blood lactate concentration of 4 mmol/l (vHla 4.0) differed markedly between the groups with the highest value (5.61 m/s) in the 5000-10,000-m group. The oxygen uptake (VO2) at vHla 4.0 in percentage of VO2 max did not differ significantly between the groups. The blood lactate concentration after exhaustion (VO2 max test) was lower in the long-distance runners. In summary, the present study demonstrates differences in physiological characteristics of elite runners specializing in different racing events. The two single (but certainly inter-related) variables in which this was most clearly seen were the maximal oxygen uptake (ml X kg-1 X min-1) and the running velocity corresponding to a blood lactate concentration of 4 mmol/l.     

Marathon performance in relation to maximal aerobic power and training indices in female distance runners.

The purpose of this study was to examine the relationships of marathon performance time (MPT) to maximal aerobic power (VO2 max), physical characteristics, and training indices recorded for 12 weeks prior to a race in 35 female distance runners. The marathon experience of the subjects ranged from two to fifteen races. Physical and aerobic power characteristics (mean +/- S.D.) were: age, 35.7 +/- 8.5 yr; height, 166.4 +/- 5.7 cm; weight, 55.1 +/- 5.7 kg; body fat, 15.7 +/- 5.0%; VO2 max, 56.5 +/- 6.2 ml . kg-1 . min-1. Marathon time for this race averaged 227.0 +/- 31.6 min. Records from individual training diaries indicated the runners averaged 71.0 +/- 10.0 workout days, 10.0 +/- 10.0 two X day-1 workouts, 81.0 +/- 8.0 total workouts, 12.3 +/- 1.8 mean km . workout-1, 5402.8 +/- 1302.6 total training min, 187.0 +/- 18.0 m . min-1 training pace, 112.2 +/- 32.1 max km . wk-1, 83.1 +/- 23.4 mean km . wk-1, 998.8 +/- 282.6 km . 12 wk-1 and 13.8 +/- 2.4 mean km . day-1. MPT was positively correlated to body mass index (r = 0.52), and body fat (r = 0.52) but negatively related to VO2 max (r = -0.65). MPT was also negatively related to previous marathons completed (r = -0.47), workout days (r = -0.47), two X day-1 workouts (r = -0.52), total workouts (r = -0.56), mean km . workout-1 (r = -0.58), total training min (r = -0.56), m . min-1, training pace (r = -0.66), max km . wk-1 (r = -0.70), mean km . wk-1 (r = -0.74), km . 12 wk-1 (r = -0.74), and mean km . day-1 (r = -0.77). MPT for our population of runners may be predicted (r = 0.82, R2 = 0.68) by the following equation: MPT, (min) = 449.88 - 7.61 (-/x km.day-1 run) - 0.63 (m.min-1, training pace); SEE = +/- 18.4 min.     

Running economy is negatively related to sit-and-reach test performance in international-standard distance runners.

The purpose of this study was to investigate the relationship between running economy (RE) and lower body flexibility. Thirty-four international-standard male distance runners (mean +/- s, age 27 +/- 5 years; body mass 64.9 +/- 4.2 kg; VO(2)max 72.8 +/- 3.7 ml x kg(-1) x min(-1)) gave written consent to participate in this study. The subjects performed an incremental treadmill test for the assessment of RE, lactate threshold and VO(2)max, and the sit-and-reach test was used to assess their general lower body and trunk flexibility. Running speeds below the lactate threshold were used to explore the relationship between running economy and sit-and-reach test performance. At 16.0 km x h(-1), the VO(2) was 50.6 +/- 3.7 ml x kg(-1) x min(-1) (range: 44.2 to 57.1 ml x kg(-1) x min(-1)). Pearson product moment correlation coefficients revealed no significant relationships between aerobic demand at 16.0 km x h(-1) and age (r = - 0.19), height (r = 0.15), body mass (r = - 0.18), or VO(2)max (r = - 0.004). However, there was a highly significant relationship between aerobic demand at 16.0 km x h(-1) and the sit-and-reach test score (r = 0.68; p < 0.0001). These results suggest that the least flexible runners are also the most economical. It is possible that stiffer musculotendinous structures reduce the aerobic demand of submaximal running by facilitating a greater elastic energy return during the shortening phase of the stretch-shortening cycle.     

A multi-stage shuttle run as a predictor of running performance and maximal oxygen uptake in adults.

The aim of this study was to assess the validity of a 20 metre multi-stage shuttle run (20-MST) as both a field test of cardiorespiratory endurance and as a predictor of competitive performance in a 10 kilometre (10 km) race. Nine male subjects (age 35.4 +/- 5.8 years) (mean +/- SD) underwent a laboratory test of maximum oxygen uptake on a treadmill (VO2 max 59.0 +/- 9.9 ml.kg.-1min-1), completed the 20-MST (score 105 +/- 23.7 laps/11.4 +/- 2.7 paliers) and competed in a 10 km race (finishing time 41.8 +/- 7.3 minutes). Analysis using Pearson's Product Moment Coefficient revealed high correlations between these variables (20-MST vs. VO2 max, r = 0.93; 20-MST vs. 10 km, r = -0.93; VO2 max vs. 10 km, r = -0.95). These results confirm that the 20-MST is a valid field test of cardio-respiratory endurance and suggest that it can additionally be used to predict relative running performance over 10 km.     

Increased training intensity effects on plasma lactate, ventilatory threshold, and endurance

The purpose of this study was to determine the effects of increased training intensity (ITI) on VO2max, plasma lactate accumulation, ventilatory threshold (VT), and performance in trained distance runners. Seven trained male distance runners increased their training intensity three d.wk-1 at 90-95% HRmax for eight wk. ITI did not alter VO2max (65.3 +/- 2.3 vs 65.8 +/- 2.4 ml.kg-1.min-1) but improved 10 km race time (means = 63 s decrease) and increased run time to exhaustion on the treadmill at the same speed and grade (means = 3.88 min). Significant decreases in plasma lactate concentration at 85 and 90% of VO2max were observed after ITI. No differences were found in plasma lactate at 65, 70, 75 or 80% of VO2max or VT following ITI. Significant correlations were obtained between 10 km race times and changes in plasma lactate at 85 and 90% of VO2max (r = 0.69 and 0.73, respectively). Lactate accumulation at both 2.5 and 4.0 mM were at a significantly greater percent of VO2max after ITI. Additionally, the changes in plasma lactate were dissociated from alterations in VT after ITI. These data indicate that previously trained runners can increase training intensity to improve endurance performance by lowering lactate at the intensity at which they trained despite no changes in VO2max and VT.     

Chronic medium-chain triacylglycerol consumption and endurance performance in trained runners.

BACKGROUND: This study was designed to assess the effects of chronic consumption of medium-chain triacylglycerols (MCT) on endurance running performance. METHODS: Experimental design: participants completed the study in a randomized, cross-over, placebo-controlled, double-blind fashion. Setting: participants were recruited from the general community to participate in this university based study. Participants: twelve trained male endurance runners (30.5+/-5.2 years of age) completed the study. Interventions: participants consumed dietary supplements containing either 56 g of corn oil (LCT) or 60 g of MCT oil daily for 2 weeks. Following each dietary phase, participants completed a maximal treadmill test followed by an endurance treadmill test in which participants ran at 85% VO2max for 30 min proceeded by 75% VO2max until exhaustion. Measures: blood was taken at rest and after 45 min of exercise to assess concentrations of lactate, glucose, beta-hydroxybutyrate (beta-HBA), free fatty acids (FFA), glycerol and triacylglycerols (TG). Performance was assessed as time to exhaustion. RESULTS: VO2max (72.0+/-8.0 vs 72.4+/- 9.0 ml x kg(-1) x min(-1)) and endurance time (99.8+/-23.5 vs 106.5+/-29.4 min) did not differ (p>0.05) between MCT and LCT trials, respectively. No differences (p>0.05) in lactate, glucose, beta-HBA, FFA, glycerol or TG were detected between trials. Respiratory exchange ratio (RER) was higher (p<0.05) at 15 min for the MCT trial (0.97+/-0.10) versus the LCT trial (0.90+/-0.20), but was similar between trials at other timepoints. CONCLUSIONS: Results indicate that chronic MCT consumption neither enhances endurance nor significantly alters performance-related metabolism in trained male runners.     

The oxygen uptake response of sprint- vs. endurance-trained runners to severe intensity running.

We compared the oxygen uptake (VO2) response of sprint- and endurance-trained runners for an exhaustive square wave run lasting approximately 2 minutes. Six sprinters and six middle- and long-distance runners each performed two exhaustive square wave runs lasting approximately 2 min and two exhaustive ramp tests. VO2 was determined breath-by-breath (QP9000; Morgan Medical, Rainham, UK) and averaged across the two repeats of each test; for the square wave test, the averaged VO2 response (excluding the first 15 s) was then modelled using a monoexponential function. Both VO2peak for the ramp test (67.5+/-3.3 vs. 54.5+/-8.5 mlxkg(-1)xmin(-1); P= 0.006) and the asymptotic VO2 for the square wave run (59.6+/-2.7 vs. 50.7+/-4.6 mlxkg(-1)xmin(-1); P= 0.002) were higher for the endurance than for the sprint group. However, as a percentage of VO2peak, this asymptotic VO2 did not differ between the groups (90.1+/-3.2% (endurance) vs. 96.2+/-9.0% (sprint); P= 0.145). Across all 12 subjects, the %VO2peak attained in the square wave run was negatively correlated with VO2peak (Pearson's r= -0.811, P= 0.001). We conclude that VO2max is more important than training history as a determinant of the %VO2max attained in exhaustive square wave running lasting approximately 2 min.     

Physiological characteristics of elite prepubertal cross-country runners.

Eight elite cross-country runners and eight normally active boys 8--11 years of age were studied. The runners were selected on the basis of success in regional and/or national championships. Two of them had the first to third fastest mile run times for their age groups in the U.S. for three years. Tests included submaximal and maximal treadmill runs, an anaerobic capacity bicycle test, a mile run, and various anthropometric measures. A best career mile run (BCM) was used for comparisons within the running group. At submaximal work levels of 5.6 and 7 mph (124, 161, and 187 meters/min) the values for heart rate (HR) and respiratory exchange ratio (R) were significantly lower for the runners than for the non-runners. The VO2max of the runners (56.6 ml kg min) was significantly higher than that of the non-runners (46.0 ml kg min). For all subjects combined, mile run time was highly correlated with percent VO2max and percent max HR at all submaximal running speeds (r greater than 0.8). The correlation coefficient between mile run time and VO2max was -0.88. Within the running group, however, BCM was unrelated to VO2max but was closely related to percent VO2max at 8 mph (213 meters/min) with 4 = 0.86, and to anaerobic capacity (r = -0.88). There were no significant differences between the groups in age, height, weight, max HR, and percent body fat. Thus the runners had higher aerobic and anaerobic capacities, and greater utilization of fat as an enrgy sustrate during submaximal work. Within the running group, anaerobic capacity and running economy were closely related to BCM time, whereas VO2max was not.     

Metabolic rate, not percent dehydration, predicts rectal temperature in marathon runners

This study was designed to determine the factors predicting the post-race rectal temperature in marathon runners. Post-race rectal temperatures of 30 recreational runners (maximum oxygen consumption (VO2max) = 58.3 +/- 5.9 ml O2.kg-1.min-1; mean +/- SD) who completed a 42.2 km marathon at 75.8% (+/- 9.3%) VO2max were measured and related to their levels of dehydration (percent mass loss), their running velocities (km.h-1), and their estimated absolute metabolic rates (1 O2.min-1) for different segments of the 42.2 km race. The influence of certain anthropometric variables was also determined. Percent mass loss during the race (2.5 +/- 1.4%), post-race rectal temperatures (38.9 +/- 0.6 degrees C), and rates of sweat loss (1.0 +/- 0.3 1.h-1) were low. There was no statistical relationship between percent mass loss and post-race rectal temperature. Post-race rectal temperatures were significantly related to the metabolic rates for the full 42.2 km and for the last 21.1 and 6 km of the race, and to the average running velocity for the last 6 km (P less than 0.05 and P less than 0.01). Average sweat rates were related to metabolic rates for 42.2 km and for the last 6 km of the race (P less than 0.05) but were unrelated to running velocity. We conclude that metabolic rate sustained during the latter section of the race, and not the level of dehydration, is the principal determinant of the post-race rectal temperature in marathon runners.     

Reproducibility of endurance performance on a treadmill using a preloaded time trial

PURPOSE: The purpose of this study was to establish a highly reproducible test to measure endurance performance in runners. METHODS: We evaluated the reproducibility of endurance performance during a 10-km time trial performed on a treadmill after a 90-min preload run at 65% of maximal oxygen uptake VO2max). After screening and a practice test, eight endurance runners (4 men, 4 women, 33.4 +/- 10.1 yr, VO2max = 60.3 +/- 6.3 mL x kg(-1) x min(-1) in men and 51.8 +/- 2.2 mL x kg(-1) x min(-1) in women, mean +/- SD) completed two preloaded time trial tests spaced 3-4 wk apart in men and one menstrual cycle apart in women. A high-carbohydrate diet (15% protein, 10% fat, 75% carbohydrate) was provided the day before both tests. RESULTS: Runners completed time trial 1 and time trial 2 in 45:41 +/- 4:45 and 45:24 +/- 5:03 min:s, respectively (43:29 +/- 5:02 and 43:12 +/- 5:14 min:s for men and 47:53 +/- 3:47 and 47:35 +/- 4:23 min:s for women, trials 1 and 2, respectively). The within-subject coefficient of variation for 10-km time was 1.00% +/- 0.25% (point estimate +/- estimated standard error) (0.54% +/- 0.19% for men and 1.26% +/- 0.45% for women). CONCLUSION: These results suggest that performance measured as time to complete a 10-km time trial on a treadmill after a 90-min preload is extremely reliable and may be useful for future research assessing the effect of diet, ergogenic substances, or training methods on endurance running performance.     

Correlations between laboratory testing and distance running performance in marathoners of similar performance ability

Correlations between distance running performance and laboratory testing were examined in 11 marathoners of similar fitness (VO2max 66.4 +/- 1.7 ml/kg X min). They performed a graded treadmill test and a subsequent 30 km cross-country run. Heart rate, oxygen intake, blood lactate, and plasma catecholamines were measured during the treadmill test. Lactate equivalent, individual lactate threshold, 4 mmol lactate threshold, submaximum (16 km/h running velocity) lactate behavior, submaximum catecholamine responses, submaximum lactate-catecholamine product, measured VO2max, and extrapolated VO2max were examined for their adequacy in the evaluation of distance running capacity. Race times and free urine catecholamines were estimated in the field experiment. Direct correlations were found between race times and minimum lactate equivalent (r = 0.69), submaximum lactate levels (r = 0.52), submaximum catecholamine responses (r = 0.69), submaximum lactate-catecholamine product (r = 0.79), respectively. Inverse correlations were observed between race times and oxygen intake at individual lactate threshold (r = -0.68), 4 mmol lactate threshold (r = -0.76), measured VO2max (r = -0.71), and extrapolated VO2max (r = -0.63). Further correlations were found between submaximum noradrenaline and lactate behavior (r = 0.53), as well as between noradrenaline and adrenaline responses (r = 0.72). No significant correlation was observed between relative heart volumes or catecholamine excretion and race times.